{
    let str='\u0062'; //0000-FFFF
    console.log(str);
}
{
    let str='\uD842\uDFB7';  //超出FFFF范围 -𠮷
    console.log(str);
}
{
    let a='123';
    let b='456';
    console.log(a+b);
}
{
    let str='\u20BB7';  //₻7
    console.log(str);
}

{
    let str='\u{20BB7}';  //𠮷
    console.log(str);
}
{
    let str='𠮷'
    console.log(str.length); //2 2个字符 4个字节
    console.log(str.charAt(0));
    console.log(str.charAt(1));
    console.log(str.charCodeAt(0).toString(16));
    console.log(str.charCodeAt(1).toString(16));
    //\uD842\uDFB7
    //console.log(str.codePointAt(0).toString(16));
    //console.log(str.codePointAt(1).toString(16));

}
{
    let str='吉';
    console.log(str.length); //1
    console.log(str.charAt(0));
}
{
    let str='𠮷a'
    // console.log(str.codePointAt(0).toString(16));
    // console.log(str.codePointAt(1).toString(16));
    // console.log(str.codePointAt(2).toString(16));
    for(let s of str){
        console.log(s.codePointAt(0).toString(16));
    }
}
{
    function demo(str){
        return str.codePointAt(0)>0xFFFF;
    }
    console.log(demo('你'));
    console.log(demo('𠮷'));
}
{
    console.log('abc'.at(0));
    console.log('𠮷'.at(0));
}